Leptosphaeria maculans, a fungal pathogen of Brassica napus, secretes a subtilisin-like serine protease

Blackleg, caused by the fungal pathogen Leptosphaeria maculans, is one of the most economically important diseases of canola (Brassica napus, oilseed rape) worldwide. This study assessed incidence of blackleg, the avirulence allele, and mating type distributions of L. maculans isolates collected in commercial canola fields in Manitoba, Canada, from 2010 to 2015. A total of 956 L. maculans isolates were collected from 2010 to 2015 to determine the presence of 12 avirulence alleles using differential canola cultivars and/or PCR assays specific for each avirulence allele. AvrLm2, AvrLm4, AvrLm5, AvrLm6, AvrLm7, AvrLm11, and AvrLmS were detected at frequencies ranging from 97 to 33%, where the AvrLm1, AvrLm3, AvrLm9, AvrLepR1, and AvrLepR2 alleles were the least abundant. When the race structure was examined, a total of 170 races were identified among the 956 isolates, with three major races, AvrLm-2-4-5-6-7-11, AvrLm-2-4-5-6-7-11-S, and Avr-1-4-5-6-7-11-(S) accounting for 15, 10, and 6% of the total fungal population, respectively. The distribution of the mating type alleles (MAT1-1 and MAT1-2) indicated that sexual reproduction was not inhibited in any of the nine Manitoba regions in any of the years L. maculans isolates were collected.

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Hormonal Responses to Susceptible, Intermediate, and Resistant Interactions in the Brassica napus–Leptosphaeria maculans Pathosystem

International Journal of Molecular Sciences ◽

10.3390/ijms22094714 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4714

Author(s):

Cunchun Yang ◽

W. G. Dilantha Fernando

Keyword(s):

Brassica Napus ◽

Plant Defense ◽

Fungal Pathogen ◽

Durable Resistance ◽

Leptosphaeria Maculans ◽

Hormone Signaling ◽

Hormonal Responses ◽

Microbe Interactions ◽

Quantitative Analyses ◽

The Relationship

Hormone signaling plays a pivotal role in plant–microbe interactions. There are three major phytohormones in plant defense: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). The activation and trade-off of signaling between these three hormones likely determines the strength of plant defense in response to pathogens. Here, we describe the allocation of hormonal signaling in Brassica napus against the fungal pathogen Leptosphaeria maculans. Three B. napus genotypes (Westar, Surpass400, and 01-23-2-1) were inoculated with two L. maculans isolates (H75 8-1 and H77 7-2), subsequently exhibiting three levels of resistance: susceptible, intermediate, and resistant. Quantitative analyses suggest that the early activation of some SA-responsive genes, including WRKY70 and NPR1, contribute to an effective defense against L. maculans. The co-expression among factors responding to SA/ET/JA was also observed in the late stage of infection. The results of conjugated SA measurement also support that early SA activation plays a crucial role in durable resistance. Our results demonstrate the relationship between the onset patterns of certain hormone regulators and the effectiveness of the defense of B. napus against L. maculans.

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Recognition of Avirulence Gene AvrLm1 from Hemibiotrophic Ascomycete Leptosphaeria maculans Triggers Salicylic Acid and Ethylene Signaling in Brassica napus

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-02-12-0033-r ◽

2012 ◽

Vol 25 (9) ◽

pp. 1238-1250 ◽

Cited By ~ 38

Author(s):

Vladimír Šašek ◽

Miroslava Nováková ◽

Barbora Jindřichová ◽

Károly Bóka ◽

Olga Valentová ◽

...

Keyword(s):

Salicylic Acid ◽

Brassica Napus ◽

Single Molecule ◽

Fungal Pathogen ◽

Leptosphaeria Maculans ◽

Defense Responses ◽

Avirulence Gene ◽

Ethylene Signaling ◽

Incompatible Interaction ◽

Biotrophic Pathogens

Interaction of a plant with a fungal pathogen is an encounter with hundreds of molecules. In contrast to this, a single molecule often decides between the disease and resistance. In the present article, we describe the defense responses triggered by AvrLm1, an avirulence gene from a hemibiotrophic ascomycete, Leptosphaeria maculans, responsible for an incompatible interaction with Brassica napus. Using multiple hormone quantification and expression analysis of defense-related genes, we investigated signaling events in Rlm1 plants infected with two sister isolates of L. maculans differentiated by the presence or absence of AvrLm1. Infection with the isolate carrying AvrLm1 increased the biosynthesis of salicylic acid (SA) and induced expression of the SA-associated genes ICS1, WRKY70, and PR-1, a feature characteristic of responses to biotrophic pathogens and resistance gene–mediated resistance. In addition to SA-signaling elements, we also observed the induction of ASC2a, HEL, and CHI genes associated with ethylene (ET) signaling. Pharmacological experiments confirmed the positive roles of SA and ET in mediating resistance to L. maculans. The unusual cooperation of SA and ET signaling might be a response to the hemibiotrophic nature of L. maculans. Our results also demonstrate the profound difference between the natural host B. napus and the model plant Arabidopsis in their response to L. maculans infection.

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Impact of a resistance gene against a fungal pathogen on the plant host residue microbiome: The case of the Leptosphaeria maculans–Brassica napus pathosystem

Molecular Plant Pathology ◽

10.1111/mpp.12994 ◽

2020 ◽

Vol 21 (12) ◽

pp. 1545-1558 ◽

Cited By ~ 1

Author(s):

Lydie Kerdraon ◽

Matthieu Barret ◽

Marie‐Hélène Balesdent ◽

Frédéric Suffert ◽

Valérie Laval

Keyword(s):

Brassica Napus ◽

Resistance Gene ◽

Fungal Pathogen ◽

Leptosphaeria Maculans ◽

Plant Host

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Comparison of non-subjective relative fungal biomass measurements to quantify the Leptosphaeria maculans—Brassica napus interaction

Plant Methods ◽

10.1186/s13007-021-00822-6 ◽

2021 ◽

Vol 17 (1) ◽

Author(s):

Wendelin Schnippenkoetter ◽

Mohammad Hoque ◽

Rebecca Maher ◽

Angela Van de Wouw ◽

Phillip Hands ◽

...

Keyword(s):

Brassica Napus ◽

Fungal Pathogen ◽

Fungal Biomass ◽

Quantitative Resistance ◽

Leptosphaeria Maculans ◽

Post Inoculation ◽

Blackleg Disease ◽

In Planta ◽

Visual Assessments ◽

Host Tissues

Abstract Background Blackleg disease, caused by the fungal pathogen Leptosphaeria maculans, is a serious threat to canola (Brassica napus) production worldwide. Quantitative resistance to this disease is a highly desirable trait but is difficult to precisely phenotype. Visual scores can be subjective and are prone to assessor bias. Methods to assess variation in quantitative resistance more accurately were developed based on quantifying in planta fungal biomass, including the Wheat Germ Agglutinin Chitin Assay (WAC), qPCR and ddPCR assays. Results Disease assays were conducted by inoculating a range of canola cultivars with L. maculans isolates in glasshouse experiments and assessing fungal biomass in cotyledons, petioles and stem tissue harvested at different timepoints post-inoculation. PCR and WAC assay results were well correlated, repeatable across experiments and host tissues, and able to differentiate fungal biomass in different host-isolate treatments. In addition, the ddPCR assay was shown to differentiate between L. maculans isolates. Conclusions The ddPCR assay is more sensitive in detecting pathogens and more adaptable to high-throughput methods by using robotic systems than the WAC assay. Overall, these methods proved accurate and non-subjective, providing alternatives to visual assessments to quantify the L. maculans-B. napus interaction in all plant tissues throughout the progression of the disease in seedlings and mature plants and have potential for fine-scale blackleg resistance phenotyping in canola.

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Recent Findings Unravel Genes and Genetic Factors Underlying Leptosphaeria maculans Resistance in Brassica napus and Its Relatives

International Journal of Molecular Sciences ◽

10.3390/ijms22010313 ◽

2020 ◽

Vol 22 (1) ◽

pp. 313

Author(s):

Aldrin Y. Cantila ◽

Nur Shuhadah Mohd Saad ◽

Junrey C. Amas ◽

David Edwards ◽

Jacqueline Batley

Keyword(s):

Brassica Napus ◽

Genetic Factors ◽

Quantitative Resistance ◽

Genetic Resistance ◽

Leptosphaeria Maculans ◽

Gene Interaction ◽

R Gene ◽

R Genes ◽

Blackleg Resistance ◽

Avr Gene

Among the Brassica oilseeds, canola (Brassica napus) is the most economically significant globally. However, its production can be limited by blackleg disease, caused by the fungal pathogen Lepstosphaeria maculans. The deployment of resistance genes has been implemented as one of the key strategies to manage the disease. Genetic resistance against blackleg comes in two forms: qualitative resistance, controlled by a single, major resistance gene (R gene), and quantitative resistance (QR), controlled by numerous, small effect loci. R-gene-mediated blackleg resistance has been extensively studied, wherein several genomic regions harbouring R genes against L. maculans have been identified and three of these genes were cloned. These studies advance our understanding of the mechanism of R gene and pathogen avirulence (Avr) gene interaction. Notably, these studies revealed a more complex interaction than originally thought. Advances in genomics help unravel these complexities, providing insights into the genes and genetic factors towards improving blackleg resistance. Here, we aim to discuss the existing R-gene-mediated resistance, make a summary of candidate R genes against the disease, and emphasise the role of players involved in the pathogenicity and resistance. The comprehensive result will allow breeders to improve resistance to L. maculans, thereby increasing yield.

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Development of an agronomically superior blackleg resistant canola cultivar in Brassica napus L. using doubled haploidy

Canadian Journal of Plant Science ◽

10.4141/cjps95-072 ◽

1995 ◽

Vol 75 (2) ◽

pp. 437-439 ◽

Cited By ~ 12

Author(s):

G. R. Stringam ◽

V. K. Bansal ◽

M. R. Thiagarajah ◽

D. F. Degenhardt ◽

J. P. Tewari

Keyword(s):

Brassica Napus ◽

Doubled Haploid ◽

Leptosphaeria Maculans ◽

Resistance Breeding ◽

Breeding Method ◽

Brassica Napus L ◽

Breeding Lines ◽

University Of Alberta ◽

Blackleg Resistance ◽

The University

The doubled haploid breeding method and greenhouse screening using cotyledon bio-assay were successfully applied to transfer blackleg resistance from the Australian cultivar Maluka (Brassicas napus), into susceptible advanced B. napus lines from the University of Alberta. This approach for blackleg resistance breeding was effective and efficient as several superior blackleg resistant breeding lines were identified within 4 yr from the initial cross. One of these lines (91–21864NA) was entered in the 1993 trials of the Western Canada Canola/Rapeseed Recommending Committee. Key words: Blackleg resistance, Leptosphaeria maculans, doubled haploid, Brassica napus

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